It is of high importance to keep down power consumption in modern radio communication equipment. Depending on the specific case this relates to cost, heat dissipation/temperature and battery life.
The transmit power amplifier accounts for a significant fraction of the total power consumption, so any improvement in its efficiency is of interest.
Advanced radio equipment normally carries waveforms spanning a significant dynamic range. At the same the emitted signal has to comply with strict frequency masks, resulting in the need for very linear amplifiers. Normally this has been achieved by employing Class A amplifiers capable of transmitting the highest signal level without significant distortion, inevitably leading to very poor power added efficiency, as the amplifier supply continuously allows for a signal of maximum amplitude.
There has been obtained some efficiency improvements by changing the power supply state as the signal level changes.